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Subject[PATCH v3 2/4] ftrace: add tracepoint for timer
This patch is modify from Mathieu's patch base on Ingo's suggestion, the
original patch can be found here:
http://marc.info/?l=linux-kernel&m=123791201816247&w=2

Great thanks to Thomas for giving me so many valuable advices.

Those tracepoints are wanted and useful:
1: We can detect a timer's delay
2: We can monitor the lifecycle and behaviors of a timer

Thus they help in analysing and debuging.

Example ftrace output:
insmod-1712 [000] 145.901459: timer_init: timer=d0ace4b4
insmod-1712 [000] 145.901469: timer_start: timer=d0ace4b4 func=timer_fun expires=4294813629 timeout=199
<idle>-0 [000] 146.100230: timer_cancel: timer=d0ace4b4
<idle>-0 [000] 146.100233: timer_expire: timer=d0ace4b4 jiffies=4294813629
<idle>-0 [000] 146.100627: timer_callback_done: func=d0ace4b4

We expect the timer expires at 4294813629, after 199 jiffies, actually the
timer expires at 4294813629, so it is delayed by 0 jiffies.
We also realize the timer's callback started at 146.100233, and it finished
at 146.100627, so it's taking 146.100627-146.100233=0.4ms.

Changelog:
v1->v2:
1: Add jiffies info into timer
2: Combine debugobjects and trace as Thomas's suggestion
v2->v3:
1: Remove function address from timer_expire and timer_cancel
as Thomas's suggestion
2: Remove debug_and_trace_timer_expire() as Thomas's suggestion
3: Rename trace_timer_entry() and trace_timer_exit() to match this patch

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
Signed-off-by: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>
---
include/trace/events/timer.h | 84 ++++++++++++++++++++++++++++++++++++------
kernel/timer.c | 31 ++++++++++++---
2 files changed, 97 insertions(+), 18 deletions(-)

diff --git a/include/trace/events/timer.h b/include/trace/events/timer.h
index ff2754a..967e225 100644
--- a/include/trace/events/timer.h
+++ b/include/trace/events/timer.h
@@ -8,52 +8,112 @@
#include <linux/timer.h>
#include <linux/hrtimer.h>

+TRACE_EVENT(timer_init,
+
+ TP_PROTO(struct timer_list *timer),
+
+ TP_ARGS(timer),
+
+ TP_STRUCT__entry(
+ __field( void *, timer )
+ ),
+
+ TP_fast_assign(
+ __entry->timer = timer;
+ ),
+
+ TP_printk("timer=%p", __entry->timer)
+);
+
+TRACE_EVENT(timer_start,
+
+ TP_PROTO(struct timer_list *timer, unsigned long expires),
+
+ TP_ARGS(timer, expires),
+
+ TP_STRUCT__entry(
+ __field( void *, timer )
+ __field( void *, function )
+ __field( unsigned long, expires )
+ __field( int, timeout )
+ ),
+
+ TP_fast_assign(
+ __entry->timer = timer;
+ __entry->function = timer->function;
+ __entry->expires = expires;
+ __entry->timeout = timer->expires - jiffies;
+ ),
+
+ TP_printk("timer=%p func=%pf expires=%lu timeout=%d", __entry->timer,
+ __entry->function, __entry->expires, __entry->timeout)
+);
+
/**
- * timer_entry - called immediately before the timer callback
+ * timer_expire - called immediately before the timer callback
* @timer: pointer to struct timer_list
*
- * When used in combination with the timer_exit tracepoint we can
+ * When used in combination with the timer_callback_done tracepoint we can
* determine the timer latency.
**/
-TRACE_EVENT(timer_entry,
+TRACE_EVENT(timer_expire,

TP_PROTO(struct timer_list *timer),

TP_ARGS(timer),

TP_STRUCT__entry(
- __field(void *, function)
+ __field( void *, timer )
+ __field( unsigned long, jiffies )
),

TP_fast_assign(
- __entry->function = timer->function;
+ __entry->timer = timer;
+ __entry->jiffies = jiffies;
),

- TP_printk("func=%pf", __entry->function)
+ TP_printk("timer=%p jiffies=%lu", __entry->timer, __entry->jiffies)
);

/**
- * timer_exit - called immediately after the timer returns
+ * timer_callback_done - called immediately after the timer returns
* @timer: pointer to struct timer_list
*
- * When used in combination with the timer_entry tracepoint we can
+ * When used in combination with the timer_expire tracepoint we can
* determine the timer latency.
**/
-TRACE_EVENT(timer_exit,
+TRACE_EVENT(timer_callback_done,

TP_PROTO(struct timer_list *timer),

TP_ARGS(timer),

TP_STRUCT__entry(
- __field(void *, function)
+ __field(void *, timer )
),

TP_fast_assign(
- __entry->function = timer->function;
+ __entry->timer = timer;
),

- TP_printk("func=%pf", __entry->function)
+ TP_printk("func=%p", __entry->timer)
+);
+
+TRACE_EVENT(timer_cancel,
+
+ TP_PROTO(struct timer_list *timer),
+
+ TP_ARGS(timer),
+
+ TP_STRUCT__entry(
+ __field( void *, timer )
+ ),
+
+ TP_fast_assign(
+ __entry->timer = timer;
+ ),
+
+ TP_printk("timer=%p", __entry->timer)
);

/**
diff --git a/kernel/timer.c b/kernel/timer.c
index 9385ad5..0f53710 100644
--- a/kernel/timer.c
+++ b/kernel/timer.c
@@ -523,6 +523,25 @@ static inline void debug_timer_activate(struct timer_list *timer) { }
static inline void debug_timer_deactivate(struct timer_list *timer) { }
#endif

+static inline void debug_and_trace_timer_init(struct timer_list *timer)
+{
+ debug_timer_init(timer);
+ trace_timer_init(timer);
+}
+
+static inline void
+debug_and_trace_timer_activate(struct timer_list *timer, unsigned long expires)
+{
+ debug_timer_activate(timer);
+ trace_timer_start(timer, expires);
+}
+
+static inline void debug_and_trace_timer_deactivate(struct timer_list *timer)
+{
+ debug_timer_deactivate(timer);
+ trace_timer_cancel(timer);
+}
+
static void __init_timer(struct timer_list *timer,
const char *name,
struct lock_class_key *key)
@@ -551,7 +570,7 @@ void init_timer_key(struct timer_list *timer,
const char *name,
struct lock_class_key *key)
{
- debug_timer_init(timer);
+ debug_and_trace_timer_init(timer);
__init_timer(timer, name, key);
}
EXPORT_SYMBOL(init_timer_key);
@@ -570,7 +589,7 @@ static inline void detach_timer(struct timer_list *timer,
{
struct list_head *entry = &timer->entry;

- debug_timer_deactivate(timer);
+ debug_and_trace_timer_deactivate(timer);

__list_del(entry->prev, entry->next);
if (clear_pending)
@@ -631,7 +650,7 @@ __mod_timer(struct timer_list *timer, unsigned long expires,
goto out_unlock;
}

- debug_timer_activate(timer);
+ debug_and_trace_timer_activate(timer, expires);

new_base = __get_cpu_var(tvec_bases);

@@ -783,7 +802,7 @@ void add_timer_on(struct timer_list *timer, int cpu)
BUG_ON(timer_pending(timer) || !timer->function);
spin_lock_irqsave(&base->lock, flags);
timer_set_base(timer, base);
- debug_timer_activate(timer);
+ debug_and_trace_timer_activate(timer, timer->expires);
internal_add_timer(base, timer);
/*
* Check whether the other CPU is idle and needs to be
@@ -987,9 +1006,9 @@ static inline void __run_timers(struct tvec_base *base)
*/
lock_map_acquire(&lockdep_map);

- trace_timer_entry(timer);
+ trace_timer_expire(timer);
fn(data);
- trace_timer_exit(timer);
+ trace_timer_callback_done(timer);

lock_map_release(&lockdep_map);

--
1.6.1.2



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